EP2117063B1 - Element d'electroluminescence organique - Google Patents

Element d'electroluminescence organique Download PDF

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Publication number
EP2117063B1
EP2117063B1 EP08704495A EP08704495A EP2117063B1 EP 2117063 B1 EP2117063 B1 EP 2117063B1 EP 08704495 A EP08704495 A EP 08704495A EP 08704495 A EP08704495 A EP 08704495A EP 2117063 B1 EP2117063 B1 EP 2117063B1
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Prior art keywords
light emitting
transporting layer
layer
electron
injecting
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EP2117063A4 (fr
EP2117063A1 (fr
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Yasuhiro Iizumi
Atsushi Oda
Junji Kido
Toshitaka Mori
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Dai Nippon Printing Co Ltd
Yamagata Promotional Organization for Ind Tech
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Dai Nippon Printing Co Ltd
Yamagata Promotional Organization for Ind Tech
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    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/15—Hole transporting layers
    • H10K50/155—Hole transporting layers comprising dopants
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/16—Electron transporting layers
    • H10K50/165—Electron transporting layers comprising dopants
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/19—Tandem OLEDs
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/30—Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/321—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3]
    • H10K85/324—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3] comprising aluminium, e.g. Alq3
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/341—Transition metal complexes, e.g. Ru(II)polypyridine complexes
    • H10K85/342—Transition metal complexes, e.g. Ru(II)polypyridine complexes comprising iridium
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
    • H10K85/622—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene containing four rings, e.g. pyrene
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
    • H10K85/624—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene containing six or more rings
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/631—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
    • H10K85/633—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom

Definitions

  • the present invention relates to an organic electroluminescence element having a structure wherein a hole injecting and transporting layer, a light emitting layer, an electron injecting and transporting layer are sequentially laminated between an anode and a cathode.
  • the organic electroluminescence element (hereinafter, “electroluminescence” may be occasionally abbreviated as “EL”) generally has a multilayer structure wherein plural layers are laminated using materials having a hole or electron injecting, transporting and blocking functions in order to achieve long-lasting life and high efficiency. Further, the organic EL element having the multilayer structure generally has a blocking layer, whichprevents penetration of holes and electrons to the counter electrode, provided between an electrode and a light emitting layer to efficiently block holes and electrons in the light emitting layer.
  • EL organic electroluminescence element
  • the organic EL elements having the multilayer structure that deterioration caused during its driving at interfaces of the respective layers will lower the luminous efficiency or will deteriorate the elements to lower its luminance.
  • charges are easily built up at interfaces with the organic EL element comprising a blocking layer so that deterioration is easily caused at interfaces and the luminance deterioration of the element is a concern.
  • the Patent Document 1 discloses a method to improve the injection properties of holes from an anode and the injection properties of electrons from the cathode, wherein an organic semiconductor layer (hole injecting and transporting layer or electron injecting and transporting layer) is constituted from one of the following: an organic compound and an oxidizing dopant, an organic compound and a reducing dopant, or an organic compound and a conducting fine particle.
  • an organic semiconductor layer hole injecting and transporting layer or electron injecting and transporting layer
  • an organic semiconductor layer is constituted from one of the following: an organic compound and an oxidizing dopant, an organic compound and a reducing dopant, or an organic compound and a conducting fine particle.
  • the organic EL element of the Patent Document 1 has the above-mentioned concerns of lowering of the luminous efficiency and the causing of deterioration of elements because an inorganic charge blocking layer (blocking layer) is provided between the organic semiconductor layer (hole injecting and transporting layer or electron injecting and transporting layer) and the organic light emitting layer.
  • an inorganic charge blocking layer blocking layer
  • the Patent Document 2 discloses a method of doping an electron accepting dopant to an organic compound layer contacting an anode, and an object thereof is to lower the energy barrier caused in injecting holes from the anode to the organic compound layer (hole injecting and transporting layer).
  • the Patent Documents 3 and 4 disclose a method of doping an electron donating dopant to an organic compound layer contacting a cathode, and their respective objects are to lower the energy barrier caused by injecting electrons from the cathode to the organic compound layer (electron injecting and transporting layer).
  • the inventors of the present invention respectively: set the ionization potential of a constituent material for an electron injecting and transporting layer and the electron affinity of a constituent material for the hole injecting and transporting layer to such, compared with the ionization potential and the electron affinity of a constituent material for the light emitting layer, that they do not prevent penetration of holes and electrons to a counter electrode; appropriately selected materials used for each of the hole injecting and transporting layer, electron injecting and transporting layer, and light emitting layer; and optimized the structure of an EL element.
  • the present inventors found out that an organic EL element having high-efficiency and long-lasting lifetime compare to those of current organic EL elements can be obtained and attained the present invention.
  • the electron affinity denotes the energy difference between an energy E(o) of a ground state molecule and an anion state energy E(-) having a minus charge, and it is expressed as "A”.
  • An electron affinity in gas condition is expressed by "Ag” by adding "g”
  • an electron affinity in solid condition is expressed by "As” by adding "s”.
  • the ionization potential denotes the energy difference between an energy E(o) of a ground state molecule and a cationic state energy E (+) having a positive charge, and it is expressed as "I".
  • an ionization potential in gas condition is expressed by "Ig” by adding "g"
  • an ionization potential in solid condition is expressed by "Is” by adding "s”.
  • the polarization energy P+ affecting the positive charge is obtained.
  • the value of P + is provided by subtracting "Is" from "Ig".
  • the polarization energy P+ affecting the positive charge and the polarization energy P- affecting the negative charge vary depending on the subject properties.
  • FIG. 1 shows a band diagram of 3-tert -butyl-9, 10-di (naphtha-2-yl) anthracene (TBADN).
  • TAADN 3-tert -butyl-9, 10-di (naphtha-2-yl) anthracene
  • the present invention provides an organic EL element comprising: an anode, a hole injecting and transporting layer formed on the anode, a light emitting layer formed on the hole injecting and transporting layer, an electron injecting and transporting layer formed on the light emitting layer, and a cathode formed on the electron injecting and transporting layer, wherein relation of Ip 2 ⁇ Ip 3 is established when an ionization potential of a constituent material for the light emitting layer is Ip 2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip 3 , and wherein a relation of Ea 1 ⁇ Ea 2 is established when an electron affinity of a constituent material for the hole injecting and transporting layer is Ea 1 and an electron affinity of the constituent material for the light emitting layer is Ea 2 , wherein each of the hole injecting and transporting layer and the electron injecting and transporting layer comprises a bipolar material which can transport a hole and an electron, and wherein the bipolar material contained in the hole
  • the relation between the ionization potential of the constituent material for the electron injecting and transporting layer and the ionization potential of the constituent material for the light emitting layer is Ip 2 ⁇ Ip 3
  • the relation between the electron affinity of the constituent material for the hole injecting and transporting layer and the electron affinity of the constituent material for the light emitting layer is Ea 1 ⁇ Ea 2
  • an organic EL element comprising: plural light emitting units, which respectively having a hole injecting and transporting layer, a light emitting layer and an electron injecting and transporting layer sequentially laminated between an anode and a cathode facing each other; and a charge generating layer formed between adjacent light emitting units, wherein a relation of Ip 2 ⁇ Ip 3 is established when an ionization potential of a constituent material for the light emitting layer is Ip 2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip 3 , and wherein a relation of Ea 1 ⁇ Ea 2 is established when an electron affinity of a constituent material for the hole injecting and transporting layer is Ea 1 and an electron affinity of the constituent material for the light emitting layer is Ea 2 , wherein each of the hole injecting and transporting layer and the electron injecting and transporting layer comprises a bipolar material which can transport a hole and an electron, and wherein the bipolar material contained in the hole
  • the relation between the ionization potential of the constituent material for the electron injecting and transporting layer and the ionization potential of the constituent material for the light emitting layer is Ip 2 ⁇ Ip 3
  • the relation between the electron affinity of the constituent material for the hole injecting and transporting layer and the electron affinity of the constituent material for the light emitting layer is Ea 1 ⁇ Ea 2
  • deterioration caused during the driving of the EL element at interfaces of the respective hole injecting and transporting layer, light emitting layer, and electron injecting and transporting layer can be avoided.
  • plural light emitting units are formed between an anode and a cathode via the charge generating layer, high luminance can be realized while maintaining the current density relatively low. Accordingly, a highly efficient, high-luminance and long-lasting organic EL element can be obtained.
  • a relation of Ip 1 ⁇ Ip 2 is preferably established when an ionization potential of the constituent material for the hole injecting and transporting layer is Ip 1 .
  • a relation of Ea 2 ⁇ Ea 3 is preferably established when an electron affinity of the constituent material for the electron injecting and transporting layer is Ea 3 .
  • each of the hole injecting and transporting layer and the electron injecting and transporting layer comprises a bipolar material which can transport holes and electrons.
  • a bipolar material which can transport holes and electrons.
  • the light emitting layer may comprise a bipolar material which can transport holes and electrons.
  • the bipolar material is preferably a distyrylarene derivative, a polyaromatic compound, one of condensed ring aromatic compounds, a carbazole derivative, or a heterocyclic compound.
  • the bipolar material is preferably 4,4'-bis(2,2-diphenyl-ethene-1-yl)diphenyl (DPVBi), spiro-4,4'-bis(2,2-diphenyl-ethene-1-yl)diphenyl (spiro-DPVBi), 4,4'-bis(carbazole-9-yl)biphenyl (CBP), 2,2',7,7'-tetrakis(carbazole-9-yl)-9,9'-spiro-bifluorene (spiro-CBP), 4,4"-di(N-carbazole)-2',3',5',6'-tetraphenyl-p-terphenyl(Cz TT), 1,3
  • the hole injecting and transporting layer preferably has a region where an oxidizing dopant is mixed into an organic compound for the hole injecting and transporting layer at an interface to at least the anode or at an interface to at least the anode and the charge generating layer
  • the electron injecting and transporting layer preferably has a region where a reducing dopant is mixed into an organic compound for the electron injecting and transporting layer at an interface to at least the cathode or at an interface to at least the cathode and the charge generating layer.
  • the oxidizing dopant is preferably a metal oxide.
  • the metal oxide is preferably MoO 3 or V 2 O 5 .
  • the reducing dopant is preferably any one of a metal, a metal compound, or an organometallic complex.
  • the metal, the metal compound, or the organometallic complex contains at least a metal selected from the group consisting of an alkali metal, an alkali earth metal and a transition metal comprising a rare-earth metal having a work function of 4.2 eV or less.
  • a second hole injecting and transporting layer may be formed between the hole injecting and transporting layer and the light emitting layer.
  • a relation of Ea 1 ⁇ Ea 4 ⁇ Ea 2 is preferably established when an electron affinity of a constituent material for the second hole injecting and transporting layer is Ea 4
  • a relation of Ip 1 ⁇ Ip 4 ⁇ Ip 2 is preferably established when an ionization potential of the constituent material for the second electron injecting and transporting layer is Ip 4 .
  • a second electron injecting and transporting layer may be formed between the electron injecting and transporting layer and the light emitting layer.
  • a relation of Ip 2 ⁇ Ip 5 ⁇ Ip 3 is preferably established when an ionization potential of a constituent material for the second electron injecting and transporting layer is Ip 5
  • a relation of Ea 2 ⁇ Ea 5 ⁇ Ea 3 is preferably established when an electron affinity of the constituent mate rial for the second electron injecting and transporting layer is Ea 5 .
  • the light emitting layer preferably comprises a host material and a light emitting dopant
  • the light emitting dopant contained in the light emitting layer preferably has distribution in its concentration.
  • the light emitting layer may comprise the host material and at least two light emitting dopants.
  • the light emitting dopant which facilitates transportation of holes than electrons and the light emitting dopant which facilitates transportation of electrons than holes into the light emitting layer holes and electrons injected to the light emitting layer can be balanced.
  • the light emitting dopant having excitation energy between the excitation energies of the host material and the light emitting dopant smooth energy movement is realized.
  • the present invention by setting the relation of the ionization potentials of the respective constituent materials for the electron injecting and transporting layer and the light emitting layer, and the relation of the electron affinities of the respective constituent materials for the hole injecting and transporting layer and the light emitting layer to the predetermined relations respectively, advantageous effects of restraining the deterioration of the hole injecting and transporting layer, the light emitting layer, and the electron injecting and transporting layer at their interfaces caused during driving of the EL element, advancing the high-efficiency and obtaining stable lifetime properties can be attained.
  • organic EL element of the present invention will be explained in detail.
  • the organic EL element of the present invention can be divided in two embodiments depending on its layer structure. Hereinafter, each embodiment will be explained.
  • An organic EL element of the first embodiment of the present invention comprises: an anode, a hole injecting and transporting layer formed on the anode, a light emitting layer formed on the hole injecting and transporting layer, an electron injecting and transporting layer formed on the light emitting layer, and a cathode formed on the electron injecting and transporting layer, characterized in that a relation of Ip 2 ⁇ Ip 3 is established when an ionization potential of a constituent material for the light emitting layer is Ip 2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip 3 , and characterized in that a relation of Ea 1 ⁇ Ea 2 is established when an electron affinity of a constituent material for the hole injecting and transporting layer is Ea 1 and an electron affinity of the constituent material for the light emitting layer is Ea 2 .
  • FIG. 2 is a schematic cross-sectional view illustrating one example of the organic EL element of the present embodiment.
  • FIGS. 3 and 4 are each a pattern diagram showing an example of the band diagram of the organic EL element shown in FIG. 2 .
  • an organic EL element 1 comprises an anode 3, a hole injecting and transporting layer 4, a light emitting layer 5, an electron injecting and transporting layer 6, and a cathode 7 sequentially laminated on a substrate 2.
  • Ea 1 the electron affinity of the constituent material for the hole injecting and transporting layer 4
  • Ea 2 the electron affinity of the constituent material for the light emitting layer 5
  • Ea 3 the electron affinity of the constituent material for the electron injecting and transporting layer 6
  • the relation of the ionization potential of the constituent material for the electron injecting and transporting layer and the ionization potential of the constituent material for the light emitting layer is Ip 2 ⁇ Ip 3
  • the relation of the electron affinity of the constituent material for the hole injecting and transporting layer and the electron affinity of the constituent material for the light emitting layer is Ea 1 ⁇ Ea 2 .
  • FIG. 5 is a schematic cross-sectional view illustrating one embodiment of the organic EL element of the present invention.
  • FIGS. 6 and 7 are each a pattern diagram showing one example of the band diagram of the organic EL element shown in FIG. 5 .
  • a second hole injecting and transporting layer 8 may be formed between a hole injecting and transporting layer 4 and a light emitting layer 5, or alternatively a second electron injecting and transporting layer 9 may be formed between an electron injecting and transporting layer 6 and a light emitting layer 5.
  • the relation may be Ip 2 >Ip 4 >Ip 1 and Ip 2 >Ip 5 >Ip 3 as shown in FIG.
  • Ip 2 Ip 4 >Ip 1
  • the ionization potential of the constituent material for the hole injecting and transporting layer 4 is Ip 1
  • the ionization potential of the constituent material for the second hole injecting and transporting layer 8 is Ip 4
  • the ionization potential of the constituent material for the light emitting layer 5 is Ip 2
  • the ionizationpotential of the constituent material for the electron injecting and transporting layer 6 is Ip 3
  • the ionization potential of the constituent material for the second electron injecting and transporting layer 9 is Ip 5 .
  • organic EL element since the relation of the ionization potentials of the respective constituent material for the electron injecting and transporting layer, second electron injecting and transporting layer, and light emitting layer is Ip 2 ⁇ Ip 5 ⁇ Ip 3 , and the relation of electron affinities of the respective constituent materials for the hole injecting and transporting layer, second hole injecting and transporting layer, and light emitting layer is Ea1 ⁇ Ea 4 ⁇ Ea 2 , similar to the above-mentioned case, deterioration at interfaces of the hole injecting and transporting layer, the second hole injecting and transporting layer, the light emitting layer, the second electron injecting and transporting layer, and the electron injecting and transporting layer caused during the driving can be restrained. Therefore, a highly efficient and long-lasting organic EL element can be obtained.
  • the bandgap energy of the constituent material for the light emitting layer is relatively big and the difference between the ionization potential of the constituent material for the hole injecting and transporting layer Ip 1 and the ionization potential of the constituent material for the light emitting layer Ip 2 is relatively big, by forming the second hole injecting and transporting layer between the hole injecting and transporting layer and the light emitting layer in such a manner so as the relation becomes Ip 1 ⁇ Ip 4 ⁇ Ip 2 , holes can be smoothly transported from the hole injecting and transporting layer to the second hole injecting and transporting layer via the light emitting layer.
  • the luminous efficiency can be improved by: (1) thickening relatively the film thickness of the light emitting layer; (2) making the relation of Ip 1 ⁇ Ip 2 ; (3) making the relation of Ea 2 ⁇ Ea 3 ; (4) making the bandgap of the light emitting dopant included in the bandgap of the host material when the light emitting layer comprises the host material and the light emitting dopant; (5) having distribution in the concentration of the light emitting dopant contained in the light emitting layer when the light emitting layer comprises the host material and the light emitting dopant; (6) forming the second hole injecting and transporting layer; and (7) forming the second electron injecting and transporting layer.
  • a relation of Ip 2 ⁇ Ip 3 is established when an ionization potential of a constituent material for the light emitting layer is Ip 2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip 3
  • a relation of Ea 1 ⁇ Ea 2 is established when an electron affinity of a constituent material for the hole injecting and transporting layer is Ea 1 and an electron affinity of the constituent material for the light emitting layer is Ea 2 .
  • the "ionization potential of the constituent material” for the respective layers denotes the ionization potential of the material constituting each layer when the respective layer is formed by a single material, and denotes the ionization potential of the host material when the respective layer is formed by a host material and a dopant.
  • the "electron affinity of the constituent material” for the respective layers denotes the electron affinity of the material constituting each layer when the respective layer is formed by a single material, and denotes the electron affinity of the host material when the respective layer is formed by a host material and a dopant.
  • the relation between the ionization potential of the constituent material for the light emitting layer and the ionization potential of the constituent material for the electron injecting and transporting layer it is sufficient if a relation of Ip 2 ⁇ Ip 3 is established when an ionization potential of a constituent material for the light emitting layer is Ip 2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip 3 . Further, it is preferable if the relation is Ip 2 >Ip 3 .
  • the difference between Ip 2 and Ip 3 varies depending on the respective constituent materials of the light emitting layer and the electron injecting and transporting layer. Specifically, it is preferable to be 0.2 eV or more.
  • the relation between the ionization potential of the constituent material for the hole injecting and transporting layer and the ionization potential of the constituent material for the light emitting layer is normally Ip 1 ⁇ Ip 2 when an ionization potential of a constituent material for the hole injecting and transporting layer is Ip 1 and an ionization potential of a constituent material for the light emitting layer is Ip 2 .
  • the relation is Ip 1 >Ip 2 . This is because by having some energy barrier, hole injection during the hole transportation from the hole injecting and transporting layer to the light emitting layer can be controlled and thereby, luminous efficiency can be improved.
  • the difference between the Ip 1 and Ip 2 varies depending on the respective constituent materials of the hole injecting and transporting layer and the light emitting layer. Specifically, it is preferable to be 0.2 eV or more. Even when the difference between the Ip 1 and Ip 2 is relatively big, holes can be transported from the hole injecting and transporting layer to the light emitting layer by relatively raising a driving voltage.
  • Ea 1 >Ea 2 the difference between Ea 1 and Ea 2 varies depending on the respective constituent materials of the hole injecting and light emitting layer. Specifically, it is preferable to be 0.2 eV or more.
  • the relation between the electron affinity of a constituent material for the light emitting layer and the electron affinity of a constituent material for the electron injecting and transporting layer is normally Ea 2 ⁇ Ea 3 when an electron affinity of a constituent material for the light emitting layer is Ea 2 and an electron affinity of a constituent material for the electron injecting and transporting layer is Ea 3 .
  • the relation is Ea 2 >Ea 3 . This is because by having some energy barrier, electron injection during the electron transportation from the electron injecting and transporting layer to the light emitting layer can be controlled and thereby, luminous efficiency can be improved.
  • the difference between Ea 2 and Ea 3 varies depending on the respective constituent materials of the light emitting layer and the electron injecting and transporting layer. Specifically, it is preferable to be 0.2 eV or more. Even when the difference between Ea 2 and Ea 3 is relatively big, electrons can be transported from the electron injecting and transporting layer to the light emitting layer by relatively raising a driving voltage.
  • the relation of the electron affinity of the hole injecting and transporting layer, the second hole injecting and transporting layer, and the light emitting layer is preferably Ea 1 ⁇ Ea 4 ⁇ Ea 2 , when the electron affinity of the constituent material for the hole injecting and transporting layer is Ea 1 , the electron affinity of the constituent material for the second hole injecting and transporting layer is Ea 4 , and the electron affinity of the constituent material for the light emitting layer is Ea 2 .
  • the relation of the ionization potentials of the hole injecting and transporting layer, the second hole injecting and transporting layer, and the light emitting layer is normally Ip 1 ⁇ Ip 4 ⁇ Ip 2
  • the ionization potential of the constituent material for the hole injecting and transporting layer is Ip 1
  • the ionization potential of the constituent material for the second hole injecting and transporting layer is Ip 4
  • the ionization potential of the constituent material for the light emitting layer is Ip 2
  • the relation is preferably Ip 1 ⁇ Ip 4 ⁇ Ip 2 .
  • the difference between Ip 1 and Ip 4 , and between IP 4 and IP 2 varies depending on the respective constituent materials of the hole injecting and transporting layer, the second hole injecting and transporting layer, and the light emitting layer. Specifically, it is preferable to be 0.2 eV or more, and even more preferably to be within the range of 0.2 eV to 0.5 eV, respectively.
  • the relation of the ionization potentials of the electron injecting and transporting layer, the second electron injecting and transporting layer, and the light emitting layer is preferably Ip 2 ⁇ Ip 5 ⁇ Ip 3 , when the ionization potential of the constituent material for the light emitting layer is Ip 2 , the ionization potential of the constituent material for the second electron injecting and transporting layer is Ip 5 , and the ionization potential of the constituent material for the electron injecting and transporting layer is Ip 3 .
  • the relation of the electron affinities of the electron injecting and transporting layer, the second electron injecting and transporting layer, and the light emitting layer is normally Ea 2 ⁇ Ea 5 ⁇ Ea 3
  • the electron affinity of the constituent material for the light emitting layer is Ea 2
  • the electron affinity of the constituent material for the second electron injecting and transporting layer is Ea 5
  • the electron affinity of the constituent material for the electron injecting and transporting layer is Ea 3
  • the relation is preferably Ea 2 ⁇ Ea 5 ⁇ Ea 3 .
  • the difference between Ea 2 and Ea 5 , and between Ea 5 and Ea 3 vary depending on the respective constituent materials of the electron injecting and transporting layer, the second electron injecting and transporting layer and the light emitting layer. Specifically, it is preferable to be 0.2 eV or more, and even more preferably to be within the range of 0.2 eV to 0.5 eV, respectively.
  • the ionization potentials and the electron affinities of the respective layers are obtained as follows. First, an ionization potential and an electron affinity of a single molecule are calculated regarding the above-mentioned constituent materials using the molecular orbital calculation software Gaussian 03 TM . Specifically, a neutral molecular structure is optimized by B3LYP/6-31g(d) using the molecular orbital calculation software Gaussian 03 TM , three sets of energy calculations of positive, negative and neutral charges are conducted by B3LYP/6-311g++(d,p), and thereby the respective ionization potentials and electron affinities of the single molecule are obtained by taking the differences thereof.
  • the ionization potentials of the respective deposited films are obtained by UPS (UVphotoelectron) or the UV photoelectron device AC-2 TM or AC-3 TM manufactured by RIKEN KEIKI CO., LTD. Then, the difference between the ionization potentials of the respective single molecules and the ionization potentials of the respective deposited films are deducted from the respective electron affinities of each single molecule, the electron affinity of the respective deposited film are calculated.
  • the ionization potentials and the electron affinities show different values between the single molecules and the solid state, which is caused by the difference in the polarization energy of the solid state.
  • the polarization energy of a solid takes the same value as the first-order approximation to the holes and to the electrons.
  • an electron affinity of a solid by obtaining a polarization energy to a hole by taking a difference between an ionization potential of a single molecule and an ionization potential of a solid, and by deducting the polarization energy value to the hole from the electron affinity of the single molecule.
  • the measurement error in the ionization potentials and the electron affinities of the deposited films is about ⁇ 0.1 eV.
  • the respective ionization potentials and the electron affinities of the deposited films thereby obtained are the ionization potentials and the electron affinities of the respective constituent materials for each layer.
  • the hole injecting and transporting layer used in the present invention is formed between the anode and the light emitting layer and has a function to stably inject or transport holes from the anode to the light emitting layer.
  • the layer may be either of a hole injecting layer having a hole injecting function or a hole transporting layer having a hole transporting function, or alternatively, a single layer having both functions of the hole injecting function and the hole transporting function.
  • the constituent material for the hole inj ecting and transporting layer is a bipolarmaterial which can transport a hole and an electron.
  • the "bipolar material” denotes a material which can stably transport both holes and electrons, is a material which can stably transport electrons when a unipolar device for electrons is manufactured by using a material doped with the reducing dopant, and is a material which can stably transport holes when a unipolar device for holes is manufactured by using a material doped with an oxidizing dopant.
  • a unipolar device for electrons are manufactured by doping Cs or 8-hydroxyquinolinolatolithium (Liq) as a reducing dopant doped in the material, and a unipolar device for holes are manufactured by doping V 2 O 5 or MoO 3 as an oxidizing dopant doped in the material.
  • a distyrylarene derivative As examples of the bipolar material, a distyrylarene derivative, a polyaromatic compound, condensed ring aromatic compounds, a carbazole derivative, and a heterocyclic compound can be cited. More specifically, 4,4'-bis(2,2-diphenyl-ethen-1-yl)diphenyl(DPVBi), spiro-4,4'-bis(2,2-diphenyl-ethen-1-yl)diphenyl(spiro-DPVBi ), spiro-6P , 4,4'-bis(carbazol-9-yl)biphenyl(CBP), 2,2',7,7'-tetrakis(carbazol-9-yl)-9,9'-spiro-bifluorene(spi ro-CBP), 4,4''-di(N-carbazolyl)-2',3',5',6'-tetraphenyl-p-terphen
  • the hole injecting and transporting layer and the electron injecting and transporting layer contain the bipolar material
  • the bipolar material contained in the hole injecting and transporting layer and the bipolar material contained in the electron injecting and transporting layer are different.
  • the hole injecting and transporting layer has a region where an oxidizing dopant is mixed into the organic compound for the hole injecting and transporting layer at an interface to at least the anode.
  • a process of injecting holes from an anode to an organic layer is a process of oxidizing the organic compound at the anode surface, i.e., a process of forming a radical cationic state ( Phys. Rev.Lett., 14, 229 (1965 )).
  • hole injecting energy barrier is small and the driving voltage can be lowered compare to the case of a conventional organic EL element.
  • Oxidizing dopant is not limited as long it has properties to oxidize an organic compound for the hole injecting and transporting layer, and an electron-accepting compound is normally used.
  • an electron-accepting compound both of an inorganic kind and an organic kind can be used.
  • the electron-accepting compound is an inorganic kind
  • ferricchloride, aluminum chloride, gallium chloride, indium chloride, antimony pentachloride, and a Lewis acid such as molybdic anhydride (MoO 3 ) and vanadium pentoxide (V 2 O 5 ) can be cited as examples.
  • a Lewis acid such as molybdic anhydride (MoO 3 ) and vanadium pentoxide (V 2 O 5 )
  • the electron-accepting compound is an organic kind
  • a substance such as trinitrofluorenone can be cited.
  • a metal oxide is preferable as an electron-accepting compound, and MoO 3 and V 2 O 5 are suitably used.
  • the hole injecting and transporting layer has a region where an oxidizing dopant is mixed into an organic compound for the hole injecting and transporting layer
  • the hole injecting and transporting layer has such region at an interface to at least the anode.
  • the oxidizing dopant may be universally doped in the hole injecting and transporting layer, the oxidizing dopant may be doped in such a manner that the amount thereof continuously increases from the light emitting layer side to the anode side, or the oxidizing dopant may be doped locally only at the interface to the anode of the hole injecting and transporting layer.
  • the ratio of the oxidizing dopant is more than above-mentioned range, similar to the above case, sufficient doping effect may not be obtained because the concentration of the oxidizing dopant in the hole injecting and transporting layer becomes far stronger than the concentration of the organic compound for the hole injecting and transporting layer so that the concentration of the organic compound for the hole injecting and transporting layer oxidized by the oxidizing dopant becomes extremely low.
  • a dry method such as such as vacuum deposition method, or sputtering
  • a wet method such as printing method, ink-jet method, spin coating method, casting method, dippingmethod, barcoatingmethod, bladecoatingmethod, roll coating method, gravure coating method, flexo printing method, and spray coating
  • a method of codepositing the organic compound for the hole injecting and transporting layer and the oxidizing dopant is preferably used.
  • the oxidizing dopant having relatively low saturated vapor pressure such as ferric chloride and indium chloride, is deposited in a crucible and can be deposited by a general resistive heating method.
  • the vapor pressure may be adjusted by controlling an orifice (opening part) such as a needle valve or a mass flow controller, or the vapor pressure may be controlled through cooling by independently making the sample holder to a structure which allows the temperature control.
  • an orifice opening part
  • the vapor pressure may be controlled through cooling by independently making the sample holder to a structure which allows the temperature control.
  • a method of mixing the oxidizing dopant to the organic compound for the hole injecting and transporting layer in such a manner that the amount thereof continuously increases from the light emitting layer side to the anode side for example, a method of continuously changing the deposition speed of the organic compound for the hole injecting and transporting layer and the oxidizing dopant may be used.
  • a thickness of the hole injecting and transporting layer is not particularly limited as long as it allows the function of injecting holes from the anode and of transporting the holes to the light emitting layer to exhibit fully.
  • the thickness can be set about 0.5 nm to 1000 nm, and is preferably within the range of 5 nm to 500 nm.
  • a thickness of the hole injecting and transporting layer doped with the oxidizing dopant is not particularly limited, and preferably is 0.5 nm or more.
  • the hole injecting and transporting layer doped with the oxidizing dopant has the organic compound for the hole injecting and transporting layer in radical cationic state even in the non-electric field state and can behave as internal charges, the thickness is not particularly limited.
  • the thickness of the hole injecting and transporting layer doped with the oxidizing dopant is made thick, there is no voltage raise in the element so that a risk of causing a short circuit can be significantly reduced by setting the distance between the anode and the cathode longer than that of a normal organic EL element.
  • An electron injecting and transporting layer used in the present invention is formed between the cathode and the light emitting layer, and has a function to stably inject or transport electrons from the cathode to the light emitting layer.
  • the electron injecting and transporting layer maybe either of an electron injecting layer having an electron injecting function and an electron transporting layer having an electron transporting function, or alternatively, may be a single layer having both functions of the electron injecting function and the electron transporting function.
  • the constituent material for the electron injecting and transporting layer is a bipolar material which can transport holes and electrons.
  • a bipolar material which can transport holes and electrons.
  • the electron injecting and transporting layer has a region where a reducing dopant is mixed into the organic compound for the electron injecting and transporting layer at an interface to at least the cathode.
  • a process of injecting electrons from a cathode to an organic layer is a process of reducing the organic compound at the cathode surface, i.e., a process of forming a radical anionic state ( Phys. Rev.Lett., 14, 229 (1965 )).
  • a reducing dopant which reduces the organic compound into the electron injecting and transporting layer which contacts to the cathode, it is possible to lower the energy barrier caused in injecting electrons from the cathode.
  • electron injecting energy barrier is small and the driving voltage can be lowered compared to the case of a conventional organic EL element.
  • a metal such as a stable Al which is generally used as a wiring material may be used for the cathode.
  • Reducing dopant is not limited as long as it has properties to reduce an organic compound for the electron injecting and transporting layer, and an electron-accepting compound is normally used.
  • a metal (metal alone), a metal compound, or an organometallic complex is preferably used.
  • a metal (metal alone), metal compound, or an organometallic complex a substance comprising at least one metal selected from the group consisting of a alkali metal, an alkaline earth metal and a transition metal comprising a rare-earth metal can be cited.
  • metal metal alone
  • Li, Na, K, Cs, Be, Mg, Ca, Sr, Ba, Y, La, Mg, Sm, Gd, Yb, and W can be cited as examples.
  • metal oxides such as Li 2 O, Na 2 O K 2 O, Rb 2 O, CS 2 O, MgO, and CaO
  • metal salts such as LiF, NaF, KF, RbF, CsF, MgF 2 , CaF 2 , SrF 2 , BaF 2 , LiCl, NaCl, KCl, RbCl, CsCl, MgCl 2 , CaCl 2 , SrCl 2 , and BaCl 2
  • LiCl, NaCl, KCl, RbCl, CsCl, MgCl 2 , CaCl 2 , SrCl 2 , and BaCl 2 can be cited as examples.
  • organometallic complexes an organic metal compound containing W and 8-hydroxyquinolinolatolithium (Liq) can be cited as examples.
  • Cs, Li and Liq are preferably used. This is because, by doping these into an organic compound for the electron injecting and transporting layer, excellent electron injecting properties can be obtained.
  • the electron injecting and transporting layer has a region where a reducing dopant is mixed into an organic compound for the electron injecting and transporting layer
  • the electron injecting and transporting layer has such region at an interface to at least the cathode.
  • the reducing dopant may be universally doped in the electron injecting and transporting layer, the reducing dopant may be doped in such a manner that the amount thereof continuously increases from the light emitting layer side to the cathode side, or the reducing dopant may be doped locally only at the interface to the cathode of the electron injecting and transporting layer.
  • the reducing dopant concentration in the electron injecting and transporting layer is not particularly limited, but it is preferably about 0.1 to 99 % by weight. If the concentration of the reducing dopant is less than the above-mentioned range, sufficient doping effect may not be obtained because the concentration of the organic compound for the electron injecting and transporting layer reduced by the reducing dopant is too low.
  • the concentration of the reducing dopant is more than above-mentioned range, similar to the above case, sufficient doping effect may not be obtained because the concentration of the reducing dopant in the electron injecting and transporting layer becomes far stronger than the concentration of the organic compound for the electron injecting and transporting layer so that the concentration of the organic compound for the electron injecting and transporting layer reduced by the reducing dopant becomes extremely low.
  • a dry method such as vacuum deposition method, and sputtering
  • a wet method such as printing method, ink-j et method, spin coating method, casting method, dipping method, bar coating method, blade coating method, roll coating method, gravure coating method, flexo printing method, and spray coating
  • printing method ink-j et method
  • spin coating method casting method
  • dipping method bar coating method
  • blade coating method roll coating method
  • gravure coating method flexo printing method
  • spray coating a dry method
  • spray coating a wet method
  • a method of codepositing the organic compound for the electron injecting and transporting layer and the reducing dopant is preferably used.
  • a method such as a spin coating or dip coating can be used as a film forming method of the electron injecting and transporting layer doped with the reducing dopant.
  • the organic compound for the electron injecting and transporting layer and the reducing dopant may be dispersed into an inactive polymer.
  • a method of mixing the reducing dopant to the organic compound for the electron injecting and transporting layer in such a manner that the amount thereof continuously increases from the light emitting layer side to the cathode side for example, a method of continuously changing the deposition speed of the organic compound for the electron injecting and transporting layer and the reducing dopant may be used.
  • a thickness of the electron injecting layer is not particularly limited as long as it allows the function of injecting electrons to exhibit fully.
  • a thickness of the electron transporting layer is not particularly limited as long as it allows the function of transporting electrons to exhibit fully.
  • a thickness of the electron injecting and transporting layer doped with the reducing dopant is not particularly limited, and preferably be within the range of 0.1 nm to 300 nm, and more preferably within the range of 0.5 nm to 200 nm.
  • the thickness is less than the above-mentioned range, sufficient doping effect may not be obtained because the amount of the organic compound for the electron injecting and transporting layer doped with the reducing dopant presented nearby to the cathode interface is small.
  • the thickness is more than the above-mentioned range, there is a risk of raising a driving voltage because the film thickness of the whole electron injecting and transporting layer is too thick.
  • a light emitting layer used in the present invention has a function to provide a place for electrons and holes to rebind and to emit light.
  • pigment base materials pigment base materials, metal complex based materials, and polymer based materials can be cited.
  • pigment based light emitting materials for example, cyclopentadiene derivatives, tetraphenyl butadiene derivatives, triphenyl amine derivatives, oxadiazol derivatives, pyrazoloquinoline derivatives, distylyl benzene derivatives, distylyl arylene derivatives, silol derivatives, a thiophene ring compound, a pyridine ring compound, perynon derivatives, perylene derivatives, oligothiophene derivatives, triphmanyl amine derivatives, coumalin derivatives, an oxadiazol dimer, and a pyrazoline dimer, can be presented.
  • cyclopentadiene derivatives tetraphenyl butadiene derivatives, triphenyl amine derivatives, oxadiazol derivatives, pyrazoloquinoline derivatives, distylyl benzene derivatives, distylyl arylene derivatives, silol derivative
  • metal complex based light emitting materials for example, metal complexes having Al, Zn, Be, or the like, or a rare earth metal such as Tb, Eu, Dy, or the like as the central metal, and oxadiazol, thiadiazol, phenyl pyridine, phenyl benzoimidazol, quinoline structure, or the like as the ligand, such as a aluminum quinolinol complex, a benzoquinolinol beryllium complex, a benzoxazol zinc complex, a benzothiazol zinc complex, an azomethyl zinc complex, a porphyrin zinc complex, an europium complex, an iridium metal complex, a platinum metal complex, or the like can be presented. More specifically, tris(8-hydroxyquinolinolato)aluminum (Alq3) can be used.
  • polystyrene resin for example, polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyvinyl carbazol, polyfluorenon derivatives, polyfluorene derivatives, polyquinoxaline derivatives, polydialkylfluorene derivatives, a polymer thereof, or the like can be presented. Further, those polymerizing the above-mentioned pigment base materials and the metal complex based material can also be cited.
  • the constituent material for the light emitting layer may be the bipolar material.
  • the bipolar material for the light emitting layer By using the bipolar material for the light emitting layer, deterioration caused during driving at interfaces of each of the hole injecting and transporting layer, light emitting layer, and electron injecting and transporting layer can be restrained effectively.
  • the bipolar material for the light emitting layer may be a light emitting material which itself emits fluorescence or phosphorescence, or a host material to which the light emitting dopant to be explained later is doped into. As the bipolar materials are explained in the above-mentioned section of the hole injecting and transporting layer, explanation here is omitted.
  • the light emitting layer may contain the host material such as the above-mentioned pigment base material, metal complex based material, polymer based material, and bipolar material, and the light emitting dopant.
  • the light emitting dopant for example, perylene derivatives, coumarin derivatives, rubrene derivatives, quinacrydone derivatives, squalium derivatives, porphyrin derivatives, a styryl based pigment, tetracene derivatives, pyrazoline derivatives, decacyclene, phenoxazone, quinoxaline derivatives, carbazol derivatives, and fluorene derivatives can be cited.
  • the light emitting layer contains the host material and the light emitting dopant
  • a relation of Ag h ⁇ Ag d is preferably established when an electron affinity of the host material is Ag h and an electron affinity of the light emitting dopant is Ag d
  • a relation of Ig h >Ig d is preferably established when an ionization potential of the host material is Ig h and an ionization potential of the light emitting dopant is Ig d .
  • the ionization potentials and the electron affinities of the single molecule of the host material and the light emitting dopant constituting the light emitting layer are obtained as follows.
  • an ionization potential and an electron affinity of a single molecule are calculated regarding the above-mentioned constituent materials using the molecular orbital calculation software Gaussian 03 TM .
  • a neutral molecular structure is optimized by B3LYP/6-31g(d) using the molecular orbital calculation software Gaussian 03 TM , three sets of energy calculations of positive, negative and neutral charges to the structure is conducted by B3LYP/6-311g++ (d,p), and thereby the respective ionization potentials and electron affinities are obtained by taking the differences thereof.
  • the ionization potential and the electron affinity of the deposited film shifts by the polarization energy in solid condition, but in case of the host material and the light emitting dopant, they both receive the identical polarization energy. That is, the energy level is held in the same layer while keeping the difference between the electron affinity "Ag” and the ionization potential "Ig” at molecule level.
  • the relation of the respective ionization potentials and the electron affinities of the host material and the light emitting dopant constituting the light emitting layer can be defined by the relation of the electron affinity "Ag” and the ionization potential "Ig” at molecule level.
  • the light emitting layer comprises a host material and a light emitting dopant
  • the light emitting layer preferably has distribution in its light emitting dopant concentration.
  • trapping of holes and electrons by the light emitting dopant can be controlled and it is possible to improve the luminous efficiency.
  • no blocking layer which prevents holes and electrons injected to the light emitting layer from penetrating to the counter electrode is provided, it is difficult to balance holes and electrons injected to the light emitting layer unlike a conventional organic EL element which comprise a blocking layer.
  • luminous efficiency improves by providing distribution in the light emitting dopant concentration contained in the light emitting layer.
  • a distribution in light emitting dopant concentration in the light emitting layer is not limited as long as there is a distribution in light emitting dopant concentration.
  • the a distribution in light emitting dopant concentration may have a concentration gradient which continuously changes to the thickness direction of the light emitting layer, or may have mixed regions of a region having relatively high light emitting dopant concentration and a region having relatively low light emitting dopant concentration.
  • the light emitting dopant concentration may be high at the hole injecting and transporting layer side, or at the electron injecting and transporting layer side so that injections of holes and electrons are balanced out.
  • the distribution in light emitting dopant concentration is preferably high at the hole injecting and transporting layer so that injected holes can be trapped at the anode side.
  • the distribution in light emitting dopant concentration is preferably high at the electron injecting and transporting layer so that injected electrons can be trapped at the cathode side.
  • the light emitting dopant concentration has mixed regions of a region having relatively high light emitting dopant concentration and a region having relatively low light emitting dopant concentration
  • the followings are appropriately selected so that injections of holes and electrons are balanced out, for example, : a region having relatively high light emitting dopant concentration may be provided to the hole injecting and transporting layer side and a region having relatively low light emitting dopant concentration may be provided to the electron injecting and transporting layer side; a region having relatively low light emitting dopant concentration may be provided to the hole injecting and transporting layer side, and a region having relatively high light emitting dopant concentration may be provided to the electron injecting and transporting layer side; or the light emitting dopant concentration may periodically change in the thickness direction of the light emitting layer.
  • a region having relatively high light emitting dopant concentration is provided to the hole injecting and transporting layer side and a region having relatively low light emitting dopant concentration is provided to the electron injecting and transporting layer side so that injected holes can be trapped at the anode side.
  • a region having relatively low light emitting dopant concentration is provided to the hole injecting and transporting layer side and a region having relatively high light emitting dopant concentration is provided to the electron injecting and transporting layer side so that injected electrons can be trapped at the cathode side.
  • the light emitting layer may contain the host material and at least two light emitting dopants.
  • the difference in the excitation energies of the host material and the light emitting dopant is relatively big, by further containing a light emitting dopant having excitation energy between the excitation energies of the host material and the light emitting dopant, energy is smoothly moved so that it can improve luminous efficiency.
  • a light emitting dopant which transports more easily holes compare to electrons and a light emitting dopant which transports more easily electrons than holes, holes and electrons injected to the light emitting layer can be balanced out so that luminous efficiency is improved.
  • each light emitting dopant may emit light or only one may emit light.
  • light emission of one light emitting dopant or each of the light emitting dopants can be obtained depending on the size (big or small), distribution condition (s), concentration (s) of the excitation energy of the light emitting dopant (s) : a case where the light emitting layer contains the first light emitting dopant and the second light emitting dopant which has smaller excitation energy than that of the host material and has larger excitation energy than that of the first light emitting dopant; a case where the light emitting layer contains the third light emitting dopant which transports holes more easily than electrons and the fourth light emitting dopant which transports electrons more easily than holes.
  • the light emitting layer has at least two light emitting dopants, from the point of view of improving the luminous efficiency, it is possible to have the light emitting layer contain: the first light emitting dopant and the second light emitting dopant which has smaller excitation energy than that of the host material and has larger excitation energy than that of the first light emitting dopant; or alternatively, the third light emitting dopant which transports holes more easily than electrons and the fourth light emitting dopant which transports electrons more easily than holes.
  • the first light emitting dopant and the second light emitting dopant can be appropriately selected from the above-mentioned light emitting dopants.
  • Alq3 which emits green
  • DCM which emits red
  • rubrene which emits yellow
  • energy can be smoothly moved in order of Alq3 (host material) ⁇ rubrene (second light emitting dopant) ⁇ DCM (first light emitting dopant).
  • the third light emitting dopant and the fourth light emitting dopant can be appropriately selected from the above-mentioned light emitting dopants according to the constituent materials for the hole injecting and transporting layer and the electron injecting and transporting layer, and the combination of the host materials of the light emitting layer.
  • TBADN for the host material of the light emitting layer
  • rubrene for the light emitting dopant which transports holes more easily than electrons.
  • TBADN for the host material of the light emitting layer
  • anthracenediamine for the light emitting dopant
  • anthracenediamine becomes the light emitting dopant which transports electrons more easily than holes.
  • the light emitting layer containing the host material and the light emitting dopant is a layer which transports holes more easily than electrons or is a layer which transports electrons more easily than holes can be confirmed by evaluating the angle dependency of light emitting spectrum emission pattern of the obtained organic EL element which contains the host material and a single light emitting dopant. In other words, it can be confirmed by the wavelength of the light emitting spectrum, refractive index of materials, optical path length until the light is taken out from the light emitting layer in the organic EL element and angle dependency of emission pattern.
  • the respective concentration of the third light emitting dopant and the fourth light emitting dopant preferably has concentration gradient which continuously change to the thickness direction of the light emitting layer. Further, it is also preferable that the light emitting layer has a region with relatively high concentration and a region with relatively low concentration of the respective third light emitting dopant and fourth light emitting dopant. Thereby, holes and electrons injected into the light emitting layer can be balanced out.
  • the concentration of the third light emitting dopant may be high at the hole injecting and transporting layer side and the concentration of the fourth light emitting dopant may be high at the electron injecting and transporting layer side; the concentration of the third light emitting dopant may be high at the electron injecting and transporting layer side and the concentration of the fourth light emitting dopant maybe high at the hole injecting and transporting layer side; the concentration of the third light emitting dopant and the concentration of the fourth light emitting dopant are both high at the hole injecting and transporting layer side; or the concentration of the third light emitting dopant and the concentration of the fourth light emitting dopant may be high at the electron injecting and transporting layer side.
  • the concentration of the third light emitting dopant which transports holes more easily than electrons is high at the hole injecting and transporting layer side, and the concentration of the fourth light emitting dopant which transports electrons more easily than holes is high at the electron injecting and transporting layer side. Further, it is also preferable that the concentration of the third light emitting dopant which transports holes more easily than electrons is high at the electron injecting and transporting layer side, and the concentration of the fourth light emitting dopant which transports electrons more easily than holes is high at the hole injecting and transporting layer side. Thereby, injection balance of holes and electrons can be effectively taken.
  • the light emitting layer has a region with relatively high concentration and a region with relatively low concentration of the respective third light emitting dopant and the fourth light emitting dopant, theymaybe as follows: a region having relatively high third light emitting dopant concentration is provided to the hole injecting and transporting side and a region having relatively low third light emitting dopant concentration may be provided to the electron injecting and transporting layer side; and a region having relatively low third light emitting dopant concentration may be provided to the hole injecting and transporting side and a region having relatively high third light emitting dopant concentration may be provided to the electron injecting and transporting layer side.
  • a region having relatively high fourth light emitting dopant concentration may be provided to the hole injecting and transporting side and a region having relatively low fourth light emitting dopant concentration may be provided to the electron injecting and transporting layer side; a region having relatively low fourth light emitting dopant concentration may be provided to the hole injecting and transporting side and a region having relatively high fourth light emitting dopant concentration may be provided to the electron injecting and transporting layer side.
  • a region having relatively low third light emitting dopant concentration which transports holes more easily than electrons is provided to the hole injecting and transporting side and a region having relatively high third light emitting dopant concentration is provided to the electron injecting and transporting layer side, while also a region having relatively high fourth light emitting dopant concentration which transports electrons more easily than holes is provided to the hole injecting and transporting side and a region having relatively low fourth light emitting dopant concentration is provided to the electron injecting and transporting layer side.
  • a region having relatively high third light emitting dopant concentration which transports holes more easily than electrons is provided to the hole injecting and transporting side and a region having relatively low third light emitting dopant concentration is provided to the electron injecting and transporting layer side, while also a region having relatively low fourth light emitting dopant concentration which transports electrons more easily than holes is provided to the hole injecting and transporting side and a region having relatively high fourth light emitting dopant concentration is provided to the electron injecting and transporting layer side.
  • a thickness of the light emitting layer is not particularly limited as long as it can provide a place for holes and electrons to rebind.
  • the thickness may be set about 1 nm to 200 nm.
  • the thickness of the light emitting layer is preferably within the range between 10 nm to 100 nm, and more preferably within the range between 30 nm to 80 nm.
  • a dry method such as vacuum deposition method and sputtering
  • a wet method such as printing method, ink-j et method, spin coating method, castingmethod, dippingmethod, bar coatingmethod, blade coating method, roll coating method, gravure coating method, flexo printing method, and spray coating
  • printing method ink-j et method
  • spin coating method castingmethod
  • dippingmethod bar coatingmethod
  • blade coating method roll coating method
  • gravure coating method flexo printing method
  • barrier may be formed between light emitting layers.
  • a photosetting type resin such as a photosensitive polyamide resin and an acrylate based resin, a thermal curing resin, or an inorganic material can be used. Further, a treatment to change the surface energy (wettability) of the barrier may be conducted.
  • a method of codepositing the host material and the light emitting dopant is preferably used.
  • a method of codepositing the host material and the light emitting dopant is preferably used.
  • a method such as a spin coating or dip coating can be used as a film forming method of the light emitting layer which contains the host material and the light emitting dopant.
  • the host material and the light emitting dopant may be dispersed into an inactive polymer.
  • a method of continuously or periodically changing the deposition speed of the host material and the light emitting dopant can be used for example.
  • a second hole injecting and transporting layer may be formed between the hole injecting and transporting layer and the light emitting layer.
  • the respective ionization potentials and electron affinities of the constituent materials for each of the hole injecting and transporting layer, second hole injecting and transporting layer, and light emitting layer preferably fulfill the above-mentioned relations.
  • the hole injecting and transporting layer When the second hole injecting and transporting layer may be formed between the hole injecting and transporting layer and the light emitting layer, normally, the hole injecting and transporting layer functions as the hole injecting layer and the second hole injecting and transporting layer functions as the hole transporting layer.
  • the constituent material for the second hole injecting and transporting layer is a bipolar material.
  • a bipolar material By using the bipolar materials for the second hole injecting and transporting layer, deterioration at interfaces of the light emitting layer and the second hole injecting and transporting layer during driving can be efficiently restrained.
  • the bipolar material are explained in the above-mentioned section of the hole injecting and transporting layer, explanation here is omitted.
  • the thickness and the film forming method of the second hole injecting and transporting layer are the same as those explained in the above-mentioned hole injecting and transporting layer, explanations here are omitted.
  • the second electron injecting and transporting layer may be formed between the electron injecting and transporting layer and the light emitting layer.
  • the respective ionization potentials and electron affinities of the constituent materials for the electron injecting and transporting layer, the second electron injecting and transporting layer, and the light emitting layer preferably fulfill the above-mentioned relations.
  • the electron injecting and transporting layer functions as the electron injecting layer
  • the second electron injecting and transporting layer functions as the electron transporting layer
  • the constituent material for the second electron injecting and transporting layer is a bipolar material.
  • the bipolar material for the second electron injecting and transporting layer By using the bipolar material for the second electron injecting and transporting layer, deterioration at the interfaces of the light emitting layer and the second electron injecting and transporting layer during driving can be effectively restrained.
  • the bipolar material is explained in the above-mentioned section of the hole injecting and transporting layer, explanation here is omitted.
  • An anode used in the present invention may be transparent or opaque. When taking the light out from the anode side, the anode needs to be a transparent electrode.
  • the anode it is preferable to use a conductive material having a large work function for facilitating the hole injection. Further, it is preferable that the anode has a resistance as small as possible and a metal material is generally used therefor.
  • Organic or inorganic compounds can also be used. Specifically, tin oxide, indium tin oxide (ITO), indium oxide and the like can be cited.
  • the anode can be formed by a general electrode forming method. For example, methods such as a sputtering method, vacuum deposition method, and ion-plating method can be cited. Further, a thickness of the anode is appropriately selected depending on the resistance value and visible light transmission targeted, and a kind of the conductive material.
  • a cathode used in the present invention may be transparent or opaque. When taking the light out from the cathode side, the cathode needs to be a transparent electrode.
  • the cathode it is preferable to use a conductive material having a small work function for facilitating the electron injection. Further, it is preferable that the cathode has a resistance as small as possible and a metal material is generally used therefor.
  • Organic or inorganic compounds can also be used. Specifically, Al, Cs or Er can be cited as an example of a single compound; MgAg, AlLi, AlMg and CsTe can be cited as an example of an alloy; and Ca/Al, Mg/Al, Li/Al, Cs/Al, Cs 2 O/Al, LiF/Al, and ErF 3 /Al can be cited as an example of a laminate.
  • Cathode can be formed by a general electrode forming method. For example, methods such as a sputtering method, vacuum deposition method, and ion-plating method can be cited. Further, a thickness of the cathode is appropriately selected depending on the resistance value and visible light transmission targeted, and a kind of the conductive material.
  • a substrate of the present invention is to support members such as the above-mentioned anode, hole injecting and transporting layer, light emitting layer, electron injecting and transporting layer, and the cathode.
  • the anode or the cathode may function as the substrate, however, the anode or the cathode is normally formed on the substrate which has the predetermined strength.
  • an organic EL element can be more stably laminated from the anode side.
  • an organic EL element is normally laminated in the order of an anode, a hole injecting and transporting layer, a light emitting layer, an electron injecting and transporting layer, and a cathode on a substrate.
  • the cathode used in the present invention may be transparent or opaque.
  • the substrate needs to be a transparent substrate.
  • a transparent substrate for example, a glass substrates such as a soda lime glass, an alkaline glass, a lead alkaline glass, a borosilicate glass, an alumino silicate glass, and a silica glass; or a resin substrate capable of being shaped as a film can be cited.
  • An organic EL element of the second embodiment of the present invention comprises: plural light emitting units, which respectively having a hole injecting and transporting layer, a light emitting layer and an electron injecting and transporting layer sequentially laminated, between an anode and a cathode facing each other; and a charge generating layer formed between adjacent light emitting units, characterized in that a relation of Ip 2 ⁇ Ip 3 is established when an ionization potential of a constituent material for the light emitting layer is Ip 2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip 3 , and characterized in that a relation of Ea 1 ⁇ Ea 2 is established when an electron affinity of a constituent material for the hole injecting and transporting layer is Ea 1 and an electron affinity of the constituent material for the light emitting layer is Ea 2 .
  • FIG. 8 is a schematic cross-sectional view illustrating an example of the organic EL element of the present embodiment.
  • FIG. 9 is an explanation diagram illustrating the action mechanism of the organic EL element shown in FIG. 8 .
  • an organic EL element 1 comprises an anode 3, a light emitting unit 10a, a charge generating layer 11a, a light emitting unit 10b, a charge generating layer 11b, a light emitting unit 10c and a cathode 7 sequentially laminated on a substrate 2.
  • the light emitting units and the charge generating layers are repeatedly formed between the anode and the cathode.
  • holes (h) are injected from the anode side and electrons (e) are injected from the cathode side, and holes and electrons injected are rebound in a light emitting unit to generate an excited state and emit light.
  • three light emitting units 10a, 10b and 10c are laminated via charge generating layers 11a and 11b.
  • holes (h) are injected from the anode 3 side and electrons (e) are injected from the cathode 7 side.
  • holes (h) are injected to the cathode 7 direction by the charge generating layers 11a and 11b, and electrons (e) are injected to the anode 3 direction. Holes and electrons injected are rebound in each of the light emitting units 10a, 10b and 10c, and plural light emissions are generated between the anode 3 and the cathode 7.
  • each of the light emitting units 10a, 10b and 10c has a hole injecting and transporting layer 4, alight emitting layer 5 and an electron injecting and transporting layer 6 laminated in this order from the anode 3 side.
  • the hole injection denotes a generation of radical cation caused by a withdrawal of electrons from the valence band of a layer. Electrons withdrawn from the valence band of the hole injecting and transporting layer contacting to the cathode side of the charge generating layer is reutilized for generating the light emitting-excited state by being injected into the conductive band of the electron injecting and transporting layer contacting to the anode side of the charge generating layer.
  • the charge generating layer by respectively shifting the radical anion state (electrons) and the radical cationic state (holes) to the anode direction and to the cathode direction when voltage is applied, electrons are injected to the light emitting unit contacting to the anode side of the charge generating layer and holes are injected to the light emitting unit contacting to the cathode side of the charge generating layer.
  • each light emitting units when a voltage is applied between the anode and the cathode, each light emitting units is connected in-line and simultaneously emits light so that a high current efficiency can be realized.
  • an organic EL element having a single light emitting unit having a structure where a single light emitting unit is sandwiched between an anode and a cathode (hereinafter, referred as an organic EL element having a single light emitting unit)
  • summation of the quantum efficiency of the each light emitting units laminated via the charge generating layer (in this case, defined as the ratio between the electrons (number) (apparently) passing through each light emitting units/second and the photons (number) discharged from each light emitting units/second) becomes the quantum efficiency of the organic EL element obtained in the present embodiment so that there is no upper limit to the value thereof.
  • the organic EL element of the present embodiment can realize, for example, nth luminance without raising the current density by making the number of the light emitting units having the same structure presented in between the anode and the cathode "n" when nth luminance is aimed at a desired current density. The nth luminance can be realized without sacrificing the lifetime of the organic EL element.
  • a power conversion efficiency (W/W) is lowered by the elevation of a driving voltage.
  • a power conversionefficiency (W/W) does not change in principle because, when "n" units of the light emitting unit are to be presented between the anode and the cathode, other factors such as a light emission starting voltage (turn on Voltage) also becomes nearly nth, and quantum efficiency (current efficiency) becomes nearly nth although a voltage to obtain a desired luminance also becomes nearly nth.
  • the present embodiment also has an advantage to reduce the risk of causing element short circuit because plural layers of the light emitting units exist.
  • the organic EL element having a single light emitting unit since it has only one light emitting unit, there is a risk of instantly becoming a non-light emitting element when an (electric) short circuit is occurred between the anode and the cathode by factors such as the influence of pinhole presented in the light emitting unit.
  • a risk of short circuit can be lowered because it is thick since plural light emitting units are laminated between the anode and the cathode.
  • the organic EL element is driven by constant current, the driving voltage is only lowered by the amount of the short circuited-light emitting unit(s) so that other light emitting units not short circuited can emit light in normal order.
  • the organic EL element of the present embodiment is advantageous.
  • the above-mentioned characteristics work very advantageously for the case of using the organic EL element to emit light uniformly in a large area, in particular the case of using the element for lightning.
  • the specific resistance of the transparent electrode material (to 10 -4 ⁇ ⁇ cm) such as an electrode material, particularly typified by ITO, is higher by about double-digit compared to the specific resistance of a metal (to 10 -6 ⁇ ⁇ cm).
  • V voltage
  • E electric field
  • FIGS. 10A and 10B are each a pattern diagram showing one example of the band diagram of the light emitting unit of the organic EL element shown in FIG. 8 .
  • the relation of the ionization potentials of the respective constituent material for the electron injecting and transporting layer and light emitting layer is Ip 2 ⁇ Ip 3
  • the relation of electron affinities of the respective constituent materials for the hole injecting and transporting layer and transporting layer and light emitting layer is Ea 1 ⁇ Ea 2
  • deterioration at interfaces of the hole injecting and transporting layer, the light emitting layer, and the electron injecting and transporting layer caused during the driving can be restrained. Therefore, a highly efficient and long-lasting organic EL element can be obtained.
  • a second hole injecting and transporting layer 8 may be formed between the hole injecting and transporting layer 4 and the light emitting layer 5 as shown in FIG. 11 , or a second electron injecting and transporting layer 9 may be formed between the electron injecting and transporting layer 6 and the light emitting layer 5.
  • FIGS. 12A and 12B are each a pattern diagram showing one example of the band diagram of the light emitting unit of the organic EL element shown in FIG. 11 .
  • organic EL element since the relation of the ionization potentials of the respective constituent material for the electron injecting and transporting layer, second electron injecting and transporting layer, and light emitting layer is Ip 2 ⁇ Ip 5 ⁇ Ip 3 , and the relation of electron affinities of the respective constituent materials for the hole injecting and transporting layer and transporting layer, second hole injecting and transporting layer, and light emitting layer is Eal 1 ⁇ Ea 4 ⁇ Ea 2 , similar to the above-mentioned case, deterioration at interfaces of the hole injecting and transporting layer, second hole injecting and transporting layer, light emitting layer, second electron injecting and transporting layer, and electron injecting and transporting layer caused during the driving can be restrained. Therefore, a highly efficient and long-lasting organic EL element can be obtained.
  • the bandgap energy of the constituent material for the light emitting layer is relatively big, and the difference between the ionization potential of the constituent material for the hole injecting and transporting layer Ip 1 and the ionization potential of the constituent material for the light emitting layer Ip 2 is relatively big, by forming the second hole injecting and transporting layer between the hole injecting and transporting layer and the light emitting layer in such a manner so as the relation becomes Ip 1 ⁇ Ip 4 ⁇ Ip 2 , holes can be smoothly transported from the hole injecting and transporting layer to the second hole injecting and transporting layer via the light emitting layer.
  • the light emitting positions are separated intermittently and presented by plural numbers.
  • interference effect becomes remarkable as the element thickness becomes thicker so that there has been a problem that the color tone (that is, the emission spectrum shape) changes a lot. More specifically, the emission spectrum shape is changed, or the luminous efficiency is substantially dropped or the angle dependency is caused in emission pattern as a result of the emission at the emission peak position is canceled out by the pronounced interference effect.
  • problems associated with the interference effect can be resolved by controlling the optical thickness between the light emitting positions and the reflecting electrode.
  • organic EL element has a tendency to lower its luminance by the interference effect because the optical path length changes in terms of luminance from a tilt angle.
  • holes and electrons unlike the conventional organic EL element where holes and electrons dominantly rebind at an interface between the light emitting layer and the blocking layer, holes and electrons rebind in the whole light emitting layer so that it can improve the viewing angle dependency of the emission color compare to the conventional multi-photon emission.
  • a charge generating layer denotes an electric insulating layer having the predetermined specific resistance, which injects holes to the cathode direction and electrons to the anode direction of the element when a voltage is applied.
  • the charge generating layer has the specific resistance of 1.0 ⁇ 10 2 ⁇ ⁇ cm or more, and more preferably of 1.0 ⁇ 10 5 ⁇ ⁇ cm or more.
  • the charge generating layer preferably has the visible light transmission of 50 % or more. This is because, when the visible light transmission is less than the above-mentioned range, the generated light is to be absorbed when it transmits through the charge generating layer so that there is a possibility that the desired quantum efficiency (current efficiency) may not be obtained even if the organic EL element has plural light emitting units.
  • a material used for the charge generating layer is not particularly limited as long as the material has the above-mentioned specific resistance.
  • An inorganic or organic material can be used therefore.
  • the charge generating layer contains two different substances which can form by oxidation-reduction reaction a charge-transfer complex made of a radical cation and a radical anion. Between these two substances, a charge-transfer complex made of a radical cation and a radical anion is formed by oxidation-reduction reaction.
  • a radical cationic state (holes) and the radical anionic state (electrons) of the charge-transfer complex respectively moving to the cathode direction or anode direction when a voltage is applied, holes are injectedto a light emitting unit contacting to the cathode side of the charge generating layer and electrons are injected to a light emitting unit contacting to the anode side of the charge generating layer.
  • the charge generating layer may be a layer wherein layers respectively made of these two different substances are laminated, or a single layer which contains the two different substances.
  • the two different substances used for the charge generating layer is preferably: (a) an organic compound whose ionization potential is smaller than 5.7 eV and has hole transportation properties, i.e., electron donating properties, and (b) an inorganic or organic material which can form a charge-transfer complex by oxidation-reduction reaction with the above-mentioned organic compound (a). Further, a charge-transfer complex is preferably formed by oxidation-reduction reaction between the (a) and (b) components.
  • the two substances constituting the charge generating layer can form the charge-transfer complex by oxidation-reduction reaction by oxidation-reduction reaction can be confirmed by a spectrographic analysis. More specifically, when a mixed film of the two substances shows its peak in absorbing spectrum within the near-infrared area of wavelength of 800 nm to 2000 nm, even if each of the two substances alone does not show its peak in absorbing spectrum within the near-infrared area of wavelength of 800 nm to 2000 nm, formation of the charge-transfer complex by oxidation-reduction reaction between the two substances can be confirmed as a presence (evidence) clearly suggesting the electron movements between the two substances.
  • the ionization potential of the organic compound of (a) component is sufficient if it is smaller than 5.7 eV. This is because, in general, an ionization potential smaller than 5.7 eV is preferable for the organic compound having electron donating properties to easily become a radical cationic state.
  • an ionization potential of the organic compound of (a) component is 5.7 eV or larger, it becomes difficult to cause oxidation-reduction reaction with the substance of (b) component so that formation of charge-transfer complex may become also difficult.
  • an arylamine compound As an example of the organic compound of (a) component, an arylamine compound can be cited.
  • the arylamine compound preferably has a structure shown in below formula (1).
  • Ar 1 , Ar 2 and Ar 3 each represent independently an aromatic hydrocarbon group which may have a substituent.
  • arylamine compound for example, those arylamine compounds disclosed in the Japanese Patent Application Publication (JP-A) No. 2003-272860 can be used.
  • substance of (b) component for example, substances such as V 2 O 5 , Re 2 O 7 , and 4F-TCNQ can be cited.
  • the substance of (b) component may be a material used for the hole injecting and transporting layer.
  • the charge generating layer is further explained in detail in JP-A No. 2003-272860 .
  • Light emitting units of the present embodiment are formed by plural numbers between an anode and a cathode facing each other, and are units, each of which has the hole injecting and transporting layer, light emitting layer and electron injecting and transporting layer laminated sequentially. Further, the respective ionization potentials and the respective electron affinity of constituent materials for each of the hole injecting and transporting layer, light emitting layer, and electron injecting and transporting layer constituting a light emitting unit fulfills the predetermined relations.
  • the second hole injecting and transporting layer may be formed between the light emitting layer and the hole injecting and transporting layer.
  • the respective ionization potentials and the respective electron affinity of constituent materials for each of the hole injecting and transporting layer, second hole injecting and transporting layer, and light emitting layer fulfills the predetermined relations.
  • the second electron injecting and transporting layer may be formed between the light emitting layer and the electron injecting and transporting layer. In this case, it is preferable that the respective ionization potentials and the respective electron affinity of constituent materials for each of the electron injecting and transporting layer, second electron injecting and transporting layer, and light emitting layer fulfills the predetermined relations.
  • hole injecting and transporting layer As the light emitting layer, hole injecting and transporting layer, electron injecting and transporting layer, second hole injecting and transporting layer and second electron injecting and transporting layer are the same as those explained in the first embodiment, explanation here is omitted.
  • plural light emitting units are formed via the charge generating layer.
  • the number of lamination is not particularly limited as long as it is plural, that is at least two, and for example, it may be three layers, four layers or more.
  • the number of the lamination is preferably the kind that a high luminance can be obtained.
  • each light emitting unit may be identical or different.
  • three light emitting units each of which emits red, green, and blue lights can be laminated.
  • white light is generated.
  • an organic EL element emitting such white light for usages such as lightings a high luminance provided by large area can be obtained.
  • the respective emission strength and color phase of each light emitting unit is selected by combination so as a white light or a light close to white is generated.
  • Combination of the light emitting units which can generate a light that can be seen as white are many other than the above-mentioned combination of red, green, and blue lights. For example, combinations of blue and yellow lights, red and cyan lights, or green and magenta lights can be cited.
  • White light can be generated accordingly by using two light emitting units each of which emits each color. Further, an organic EL element can be obtained by using plural numbers of these combinations.
  • an organic EL element which generates blue light can be applied to a color display device by using a color conversion system.
  • a blue light emitting material has a short lifetime
  • the organic EL element of the present embodiment is highly efficient and has a long lifetime, it is advantageous for such a color display device.
  • the present invention is not limited to the above-mentioned embodiments.
  • the embodiments are merely examples, and any one having the substantially same configuration as the technological idea disclosed in the claims of the present invention and the same effects is included in the technological scope of the present invention.
  • the above-mentioned ionization potential Ig of a monomolecule and electron affinity Ag of a monomolecule are used as explained in the above-mentioned section of "4. Light Emitting Layer" of the first embodiment.
  • the above-mentioned ionization potential Is and the electron affinity As contain a measurement error of ⁇ 0.1eV.
  • Example 1 is a comparative example wherein the bipolar material contained in the hole injecting and transporting layer is the same as the bipolar material contained in the electron injecting and transporting layer (spiro-DPVBi).
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of spiro-DPVBi and MoO 3 was formed by codeposition on the ITO substrate at a ratio by weight of 67 : 33 under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • spiro-DPVBi was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nmat the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed by vacuum deposition on the hole transporting layer using 3-tert - butyl-9,10-di(naphtha-2-yl)anthracene (TBADN) represented by the below formula (2) as the host material and rubrene represented by the below formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 1 wt% and the thickness of the film became 70 nmat the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • TBADN 3-tert - butyl-9,10-di(naphtha-2-yl)anthracene
  • a film was formed on the light emitting layer by vacuum depositing spiro-DPVBi under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was formed. Further next, a film was formed on the electron transporting layer by codepositing spiro-DPVBi and Liq represented by the below formula (4) at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 12 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron injecting layer was formed.
  • Al was deposited on the electron injecting layer as a cathode to the film thickness of 100 nm at the deposition speed of 5.0 ⁇ /sec.
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine ( ⁇ -NPD) represented by the below formula (5) and MoO 3 was formed by codeposition on the ITO substrate at a ratio by weight of 75 : 25 under the condition of vacuum degree of 10 -5 Pa, so as the total film thickness became 10 nm at the deposition speed of 1.25 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • ⁇ -NPD represented by the above formula (5) was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed by vacuum deposition on the hole transporting layer using spiro-DPVBi as the host material and rubrene represented by the below formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of spiro-DPVBi and rubrene became 1 wt% and the thickness of the film became 30nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • FIG. 13 and FIG. 14 respectively show the luminance-voltage properties and the luminous efficiency-current density of the organic EL elements obtained in Example 1 and Comparative Example 1. From organic EL elements obtained in Example 1 and Comparative Example 1, yellow emissions derived from rubrene were observed. In the organic EL element obtained in Example 1, luminous efficiency in the front luminance was 8.4 cd/A, and an external quantum calculated from the number of photons obtained by observing the light emission emitted to all angles and the number of electrons input was 2.3 %. On the other hand, in the organic EL element obtained in Comparative Example 1, although excellent luminance-voltage properties were obtained, luminous efficiency in the front luminance was 4.4 cd/A and the external quantum calculated was 1.2%.
  • the respective lifetime properties were as follows.
  • the organic EL element obtained in Example 1 maintained luminance retention of 100 % or higher for 3,700 hours, and the estimated time where the luminance dropped by half was 10,000 hours or longer.
  • the luminance of the organic EL element obtained in Comparative Example 1 dropped by half at 2000 hours.
  • An organic EL element was produced in the same manner as Example 1, except the film thickness of the hole transporting layer, light emitting layer and electron transporting layer was made to 20 nm, 35 nm and 45 nm, respectively.
  • An organic EL element was produced in the same manner as Example 1, except the film thickness of the hole transporting layer, light emitting layer and electron transporting layer was made to 30 nm, 10 nm and 60 nm, respectively.
  • FIG. 15 and FIG. 16 respectively show the luminance-voltage properties and the luminous efficiency-current density of the organic EL elements obtained in Examples 1 to 3.
  • the organic EL element obtained in Example 2 which had the film thickness of 35 nm for the light emitting layer showed excellent result in luminance-voltage properties
  • the organic EL element obtained in Example 1 which had the film thickness of 70 nm for the light emitting layer showed the most excellent luminous efficiency.
  • Example 4 is a comparative example wherein the bipolar material contained in the hole injecting and transporting layer is the same as the bipolar material contained in the electron injecting and transporting layer (spiro-DPVBi).
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of spiro-DPVBi and MoO 3 was formed by codeposition on the ITO substrate at a deposition by ratio by weight of 67 : 33 under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • spiro-DPVBi was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 10 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed by vacuum deposition on the hole transporting layer using TBADN represented by the above formula (2) as the host material and N , N , N' , N'-tetra-p-tolyl-anthracene-9,10-diamine (anthracenediamine) represented by the below formula (7) as the light emitting dopant, which was the light emitting center, under the conditions of vacuum degree of 10 -5 Pa, so as the anthracenediamine concentration of TBADN and anthracenediamine became 5 wt% and the thickness of the film became 70 nm at the deposition speed of 1.1 ⁇ /sec. Thereby, a light emitting layer was formed.
  • a film was formed on the light emitting layer by vacuum depositing spiro-DPVBi under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was formed. Further next, a filmwas formed by codepositing spiro-DPVBi and Liq represented by the above formula (4) at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 12 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron injecting layer was formed. Lastly, Al was deposited on the electron injecting layer as a cathode to the film thickness of 100 nm at the deposition speed of 5.0 ⁇ /sec.
  • FIG. 17 and FIG. 18 respectively shows the luminance-voltage properties and the luminous efficiency-current density of the organic EL element obtained in Example 4, and FIG. 19 shows its lifetime properties.
  • green emission derived from anthracenediamine was observed.
  • Luminous efficiency in the front luminance was 15 cd/A, and an external quantum calculated from the number of photons obtained by observing the light emission emitted to all angles and the number of electrons input was 4.6 %.
  • the organic EL element was driven at constant current density of 250 A/m 2 , the estimated time where the luminance dropped by half was 6,000 hours so that it was confirmed that its lifetime properties was excellent.
  • Example 4 Despite a prediction of having an injection barrier at the electron injecting and transporting layer side unlike the result of Example 1, the organic EL element of Example 4 showed improvement in luminous efficiency. FromExample 4, it was found out that a highly efficient and long-lasting organic EL element could be obtained by having Ig and Ag of the light emitting dopant in the bandgap of Ig and Ag of host material for the light emitting layer.
  • Example 5 is a comparative example wherein the bipolar material contained in the hole injecting and transporting layer is the same as the bipolar material contained in the electron injecting and transporting layer (spiro-DPVBi).
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of spiro-DPVBi and MoO 3 was formed by codeposition on the ITO substrate at a ratio by weight of 67 : 33 under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • spiro-DPVBi was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 10 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed by vacuum deposition on the hole transporting layer using TBADN represented by the above formula (2) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • a film was formed on the light emitting layer by vacuum depositing spiro-DPVBi under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was obtained. Then, a film was formed on the electron transporting layer by codepositing spiro-DPVBi and Liq represented by the above formula (4) at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 12 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron injecting layer was formed. Further next, Al was deposited to the film thickness of 2 nm at the deposition speed of 5.0 ⁇ /sec.
  • a film of ⁇ -NPD represented by the above formula (5) and MoO 3 was formed by codeposition on the Al film at a ratio by weight of 4:1 under the condition of vacuum degree of 10 -5 Pa, so as the film thickness became 20 nm at the deposition speed of 1.25 ⁇ /sec. Thereby, a charge generating layer was formed.
  • a film of spiro-DPVBi and MoO 3 was formed by codeposition on the charge generating layer by ratio at a weight of 67:33 under the condition of vacuum degree of 10 -5 Pa, so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • spiro-DPVBi was vacuum deposited on the hole injecting layer under the condition of vacuum degree of 10 -5 Pa, so as the film thickness became 18 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed by vacuum deposition on the hole transporting layer using TBADN represented by the above formula (2) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 1 wt% and the thickness of the film became 60nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • a film was formed on the light emitting layer by vacuum depositing spiro-DPVBi under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 27 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was formed. Then, a film of spiro-DPVBi and Liq represented by the above formula (4) was formed by codeposition on the electron transporting layer at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa, so as the film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Lastly, Al was deposited on the electron injecting layer as a cathode to the film thickness of 100 nm at the deposition speed of 5.0 ⁇ /sec.
  • FIG. 20 and FIG. 21 respectively show the luminance-voltage properties and the luminous efficiency-current densities of the organic EL elements obtained in Examples 1 and 5, and FIG. 22 shows their lifetime properties.
  • Luminous efficiency in the front luminance was 16.5 cd/A, and an external quantum calculated from the number of photons obtained by observing the light emission emitted to all angles and the number of electrons input was 5.0 %.
  • the organic EL element was driven at constant current density of 250 A/m 2 , the estimated time where the luminance dropped by half was 10,000 hours or more so that it was confirmed that its lifetime properties was excellent.
  • Example 6 is a comparative example wherein the bipolar material contained in the hole injecting and transporting layer is the same as the bipolar material contained in the electron injecting and transporting layer (spiro-DPVBi).
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of spiro-DPVBi and MoO 3 was formed by codeposition on the ITO substrate with the deposition at a ratio by weight of 67 : 33 under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • spiro-DPVBi was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 10 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed on the light emitting layer by vacuum depositing spiro-DPVBi under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was obtained. Then, a film was formed on the electron transporting layer by codepositing spiro-DPVBi and Liq represented by the above formula (4) at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 12 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron injecting layer was formed.
  • Al was deposited on the electron injecting layer as a cathode to the film thickness of 100 nm at the deposition speed of 5.0 ⁇ /sec. At this time, the Al film was formed in line via a shadow mask so as the Al film became orthogonal to the lines of the ITO and the emission area became 2mm ⁇ .
  • An organic EL element was produced in the same manner as Example 6, except the light emitting layer was formed as follows.
  • a film was formed on the hole transporting layer using TBADN represented by the above formula (2) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 1 wt% and the thickness of the film became 30 nm at the deposition speed of 1.0 ⁇ /sec for TBADN.
  • the deposition speed of rubrene was speeded up so as the rubrene concentration went up from 1 wt% to 3 wt% and the film was formed into the thickness of 10 nm, and further, the film was formed into the thickness of 30 nm so as the rubrene concentration became 3 wt%. Thereby, a light emitting layer was formed.
  • An organic EL element was produced in the same manner as Example 6, except the light emitting layer was formed as follows.
  • a film was formed on the hole transporting layer using TBADN represented by the above formula (2) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 3 wt% and the thickness of the film became 30 nm at the deposition speed of 1.0 ⁇ /sec for TBADN.
  • the deposition speed of rubrene was slowed down so as the rubrene concentration went down from 3 wt% to 1 wt% and the film was formed into the thickness of 10 nm, and further, the film was formed into the thickness of 30 nm so as the rubrene concentration became 1 wt%. Thereby, a light emitting layer was formed.
  • An organic EL element was produced in the same manner as Example 6, except the light emitting layer was formed as follows.
  • a film was formed on the hole transporting layer using TBADN represented by the above formula (2) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 3 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec for TBADN. Thereby, a light emitting layer was formed.
  • FIG. 23 and FIG. 24 respectively show the luminance-voltage properties and the luminous efficiency-current density of the organic EL elements obtained in Examples 6 to 9.
  • Table 2 shows luminous efficiency, external quantum, and lifetime of the organic EL elements obtained in Examples 6 to 9.
  • Example 10 is a comparative example wherein the bipolar material contained in the hole injecting and transporting layer is the same as the bipolar material contained in the electron injecting and transporting layer (spiro-DPVBi).
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of spiro-DPVBi and MoO 3 was formed by codeposition on the ITO substrate at a deposition by ratio by weight of 67 : 33 under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • spiro-DPVBi was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 10 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed on the hole transporting layer using TBADN represented by the above formula (2) as the host material and rubrene represented by the above formula (3) and anthracenediamine represented by the above formula (7) as the light emitting dopant, which were the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of TBADN and rubrene became 1 wt% and the thickness of the film became 35 nm while also the anthracenediamine concentration of TBADN and anthracenediamine became 10 wt% and the thickness of the film became 35 nm, at the deposition speed of 1.0 ⁇ /sec for TBADN. Thereby, a light emitting layer was formed.
  • a film was formed on the light emitting layer by vacuum depositing spiro-DPVBi under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 20 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was obtained. Further next, a film was formed on the electron transporting layer by codepositing spiro-DPVBi and Liq represented by the above formula (4) at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 12 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron injecting layer was formed.
  • Al was deposited on the electron injecting layer as a cathode to the film thickness of 100 nm at the deposition speed of 5.0 ⁇ /sec. At this time, the Al film was formed in line via a shadow mask so as the Al film became orthogonal to the lines of the ITO and the emission area became 2mm 2 .
  • An organic EL element was produced in the same manner as Example 10, except the light emitting layer was formed as follows.
  • a film was formed on the hole transporting layer using TBADN represented by the above formula (2) as the host material and anthracenediamine represented by the above formula (7) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the anthracenediamine concentration of TBADN and anthracenediamine became 10 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec for TBADN. Thereby, a light emitting layer was formed.
  • FIG. 25 and FIG. 26 respectively show the luminance-voltage properties and the luminous efficiency-current density of the organic EL element obtained in Example 10, and FIG. 27 shoes the lifetime properties.
  • Table 3 shows luminous efficiency, external quantum, lifetime of the organic EL elements obtained in Examples 6, 10 and 11.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using BAlq(Bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)alum inium) represented by the below formula (8) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of BAlq and rubrene became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using CBP represented by the below formula (9) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the conditions of vacuum degree of 10 -5 Pa, so as the rubrene concentration of CBP and rubrene became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using spiro-6P represented by the below formula (10) as the host material and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the rubrene concentration of spiro-6P and rubrene became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was obtained.
  • Table 4 shows luminous efficiencies in the front luminance, external quanta calculated from the number of photons obtained by observing the light emission emitted to all angles and the number of electrons input, and estimated times where the luminance dropped by half at constant current driving of 1 mA for the organic EL elements.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using TBADN represented by the above formula (2) as the host material and 2,5,8,11-Tetra-tert-butylperylene (TBPe) represented by the below formula (11) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the TBPe concentration of TBADN and TBPe became 1 wt% and the thickness of the film became 70 nmat the deposition speedof 1.0 ⁇ /sec. Thereby, alightemitting layer was obtained.
  • TBADN represented by the above formula (2)
  • TBPe 2,5,8,11-Tetra-tert-butylperylene
  • Example 16 is a comparative example wherein the bipolar material contained in the hole injecting and transporting layer is the same as the bipolar material contained in the electron injecting and transporting layer (TBADN).
  • an ITO substrate having ITO patterned as an anode in line of 2 mm width on a glass substrate was prepared.
  • a film of TBADN and MoO 3 was formed by codeposition on the ITO substrate with the deposition at a ratio by weight of 67 : 33 under the condition of vacuum degree of 10 -5 Pa so as the total film thickness became 10 nm at the deposition speed of 1.5 ⁇ /sec. Thereby, a hole injecting layer was formed.
  • TBADN was formed on the hole injecting layer by vacuum depositing under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 10 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a hole transporting layer was formed.
  • a film was formed by vacuum deposition on the hole transporting layer using spiro-6P represented by the above formula (10) as the host material and TBPe represented by the above formula (11) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the TBPe concentration of spiro-6P and TBPe became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was formed.
  • a film was formed on the light emitting layer by vacuum depositing TBADN under the condition of vacuum degree of 10 -5 Pa so as a film thickness became 10 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron transporting layer was formed. Further next, a film was formed on the electron transporting layer by codepositing TBADN and Liq represented by the above formula (4) at a ratio by weight of 1:1 under the condition of vacuum degree of 10 -5 Pa so as the film thickness became 12 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, an electron injecting layer was formed. Lastly, Al was deposited on the electron injecting layer as a cathode to the film thickness of 100 nm at the deposition speed of 5.0 ⁇ /sec.
  • Table 5 shows luminous efficiencies in the front luminance, external quanta calculated from the number of photons obtained by observing the light emission emitted to all angles and the number of electrons input, and estimated times where the luminance dropped by half at constant current driving of 1 mA for the organic EL elements.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using TBADN represented by the above formula (2) as the host material and DCJTB represented by the below formula (12) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as the DCJTB concentration of TBADN and DCJTB became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was obtained.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using TBADN represented by the above formula (2) as the host material and DCJTB represented by the above formula (12) and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the conditions of vacuum degree of 10 -5 Pa, so as both of the DCJTB concentration and rubrene concentration of TBADN, DCJTB and rubrene became 1 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was obtained.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows. Films were formed by vacuum deposition on the hole transporting layer using spiro-6P represented by the above formula (10) as the host material and TBPe represented by the above formula (11) and rubrene represented by the above formula (3) as the light emitting dopant, which was the light emitting center, under the condition of vacuum degree of 10 -5 Pa, so as: the TBPe concentration of spiro-6P and TBPe became 1 wt% and the thickness of the film became 35 nm at the deposition speed of 1.0 ⁇ /sec for the first film; and the rubrene concentration of spiro-6P and rubrene became 1 wt% and the thickness of the film became 35 nm at the deposition speed of 1.0 ⁇ /sec for the next film. Thereby, a light emitting layer was obtained.
  • An organic EL element was produced in the same manner as Example 1, except the light emitting layer was formed as follows.
  • a film was formed by vacuum deposition on the hole transporting layer using CBP represented by the above formula (9) as the host material and Ir(piq) 3 represented by the below formula (13) as the light emitting dopant under the condition of vacuum degree of 10 -5 Pa, so as the Ir(piq) 3 concentration of CBP and Ir(piq) 3 became 5 wt% and the thickness of the film became 70 nm at the deposition speed of 1.0 ⁇ /sec. Thereby, a light emitting layer was obtained.

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Claims (12)

  1. Elément d'électroluminescence organique (1) comprenant :
    une anode (3),
    une couche d'injection et de transport de trou (4) formée sur l'anode (3),
    une couche d'émission de lumière (5) formée sur la couche d'injection et de transport de trou (4),
    une couche d'injection et de transport d'électron (6) formée sur la couche d'émission de lumière (5), et
    une cathode (7) formée sur la couche d'injection et de transport d'électron (6),
    dans laquelle une relation Ip2≧ Ip3 est établie lorsqu'un potentiel d'ionisation d'un matériau constitutif pour la couche d'émission de lumière (5) est Ip2 et un potentiel d'ionisation d'un matériau constitutif pour la couche d'injection et de transport d'électron (6) est Ip3,
    dans lequel une relation Ea1 ≧ Ea2 est établie lorsqu'une affinité électronique d'un matériau constitutif pour la couche d'injection et de transport de trou (4) est Ea1 et une affinité électronique du matériau constitutif pour la couche d'émission de lumière (5) est Ea2,
    caractérisé en ce que chacune de la couche d'injection et de transport de trou (4) et de la couche d'injection et de transport d'électron (6) comprend un matériau bipolaire qui peut transporter un trou et un électron, et
    en ce que le matériau bipolaire contenu dans la couche d'injection et de transport de trou (4) est différent du matériau bipolaire contenu dans la couche d'injection et de transport d'électron (6).
  2. Elément d'électroluminescence organique comprenant :
    plusieurs unités d'émission de lumière (10a, 10b, 10c), qui ont respectivement une couche d'injection et de transport de trou (4), une couche d'émission de lumière (5) et une couche d'injection et de transport d'électron (6), successivement stratifiées , entre une anode (3) et une cathode (7) placés en face l'une de l'autre ; et
    une couche de génération de charge (11a, 11b) formée entre des unités d'émission de lumière (10a, 10b, 10c) adjacentes,
    dans lequel une relation Ip2 ≧ Ip3 est établie lorsqu'un potentiel d'ionisation d'un matériau constitutif pour la couche d'émission de lumière (5) est Ip2 et un potentiel d'ionisation d'un matériau constitutif pour la couche d'injection et de transport d'électron (6) est Ip3,
    dans lequel une relation Ea1 ≧ Ea2 est établie lorsqu'une affinité électronique d'un matériau constitutif pour la couche d'injection et de transport de trou (4) est Ea1 et une affinité du matériau constitutif pour la couche d'émission de lumière (5) est Ea2,
    caractérisé en ce que chacune de la couche d'injection et de transport de trou (4) et de la couche d'injection et de transport d'électron (6) comprend un matériau bipolaire qui peut transporter un trou et un électron, et
    en ce que le matériau bipolaire contenu dans la couche d'injection et de transport de trou (4) est différent du matériau bipolaire contenu dans la couche d'injection et de transport d'électron (6).
  3. Elément d'électroluminescence organique (1) selon la revendication 1 ou 2, caractérisé en ce qu'une relation Ip1 < Ip2 est établie lorsqu'un potentiel d'ionisation pour la couche d'injection et de transport de trou (4) est Ip1.
  4. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'une relation Ea2 < Ea3 est établie lorsqu'une affinité électronique du matériau constitutif pour la couche d'injection et de transport d'électron (6) est Ea3.
  5. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 4, caractérisé en ce que la couche d'émission de lumière (5) comprend un matériau bipolaire qui peut transporter un trou et un électron.
  6. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 5, caractérisé en ce que le matériau bipolaire est un dérivé de distyrylarène, un composé polyaromatique, l'un de composés aromatiques de cycle condensé, d'un dérivé de carbazole ou d'un composé hétérocyclique.
  7. Elément d'électroluminescence organique (1) selon la revendication 6, caractérisé en ce que le matériau bipolaire est le 4,4'-bis(2,2-diphényl-éthène-1-yl)diphényle (DPVBi), le spiro-4,4'-bis(2,2-diphényl-éthène-1-yl)diphényle (spiro-DPVBi), le 4,4'-bis(carbazole-9-yl)biphényle (CBP), le 2,2',7,7'-tétrakis(carbazole-9-yl)-9,9'-spiro-bifluorène (spiro-CBP), le 4, 4"-di(N-carbazole)-2',3',5',6'-tétraphényl-p-terphényle (CzTT), le 1,3-bis(carbazole-9-yl)-benzène (m-CP), le 3-tert-butyl-9,10-di(naphta-2-yl) anthracène (TBADN) ou un composé représenté la formule (1) suivante :
    Figure imgb0024
  8. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 5, caractérisé en ce que la couche d'injection et de transport de trou (4) a une région où un dopant oxydant est mélangé dans un composé organique pour la couche d'injection et de transport de trou au niveau d'une interface avec au moins l'anode (3) ou au niveau d'une interface avec au moins l'anode (3) et la couche de génération de charge (11), et
    caractérisé en ce que la couche d'injection et de transport d'électron (6) a une région où un dopant réducteur est mélangé dans un composé organique pour la couche d'injection et de transport d'électron au niveau d'une interface avec au moins la cathode (7) ou au niveau d'une interface avec au moins la cathode (7) et la couche de génération de charge (11).
  9. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 8,
    caractérisé en ce qu'une seconde couche d'injection et de transport de trou (8) est formée entre la couche d'injection et de transport de trou (4) et la couche d'émission de lumière (5),
    caractérisé en ce qu'une relation Ea1 ≧ Ea4 ≧ Ea2 est établie lorsqu'une affinité électronique d'un matériau constitutif pour la seconde couche d'injection et de transport de trou (8) est Ea4,
    caractérisé en ce qu'une relation Ip1 > Ip4 > Ip2 est établie lorsqu'un potentiel d'ionisation du matériau constitutif pour la seconde couche d'injection et de transport de trou (8) est Ip4, et caractérisé en outre en ce que la seconde couche d'injection et de transport de trou (8) comprend un matériau bipolaire qui peut transporter un trou et un électron.
  10. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 9,
    caractérisé en ce qu'une seconde couche d'injection et de transport d'électron (9) est formée entre la couche d'injection et de transport d'électron (6) et la couche d'émission de lumière (5),
    caractérisé en ce qu'une relation Ip2 ≧ Ip5 ≧ Ip3 est établie lorsqu'un potentiel d'ionisation d'un matériau constitutif pour la seconde couche d'injection et de transport d'électron (9) est Ip5,
    caractérisé en ce qu'une relation Ea2 < Ea5 < Ea3 est établie lorsqu'une affinité électronique du matériau constitutif pour la seconde couche d'injection et de transport d'électron (9) est Ea5, et caractérisé en outre en ce que la seconde couche d'injection et de transport d'électron (9) comprend un matériau bipolaire qui peut transporter un trou et un électron.
  11. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 10, caractérisé en ce que la couche d'émission de lumière (5) comprend un matériau hôte et un dopant d'émission de lumière, et caractérisé en ce que le dopant d'émission de lumière contenu dans la couche d'émission de lumière a une répartition dans sa concentration.
  12. Elément d'électroluminescence organique (1) selon l'une quelconque des revendications 1 à 11, caractérisé en ce que la couche d'émission de lumière (5) comprend un matériau hôte et au moins deux dopants d'émission de lumière.
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TWI458382B (zh) 2014-10-21
CN101611505A (zh) 2009-12-23
TW200847837A (en) 2008-12-01
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JPWO2008102644A1 (ja) 2010-05-27
WO2008102644A1 (fr) 2008-08-28
US20100096622A1 (en) 2010-04-22
KR20090121317A (ko) 2009-11-25
JP5380275B2 (ja) 2014-01-08
KR101445418B1 (ko) 2014-09-26
US9000419B2 (en) 2015-04-07
EP2117063A1 (fr) 2009-11-11

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